The present invention relates to apparatus for rapidly continuously folding twofold cut pieces of a web or sheet-like material having an appreciable degree of air permeability, such as paper, non-woven fabric and so forth. More particularly, the invention concerns an improved web folding apparatus by which pieces of the material web, suitably cut to the prescribed length and successively supplied in pairs, are alternately folded, transversely in a manner such that each folded piece is in an intermeshing relation to its immediately preceding piece folded as well as its immediately succeeding piece.
Today, web folding machines of the mentioned type are widely in use, for example, in the manufacture of folded and compactly packed tissue papers typically for toilet use. In principle, these machines comprise such a structure in which there are provided a pair of rolls suitably driven for rotation, each roll having therein mounted at least one vise member and one tacker member. In operation, the tacker on one roll is engaged with the vise on the other roll at the prescribed point of the rotation of rolls, and presses the web piece into the mouth formed by the pair of jaws of the vise which initially are in open condition, to impart fold to the web. Then, the web held by the pair of jaws which are then closed is advanced along its path until rolls are rotated to reach a second prescribed point of rotation, at which the closed jaws are opened to release the web, completing the folding operation.
A difficulty indicated with this structure is that the rolls are complex and accordingly expensive to manufacture. Not only in theory alone but also in actuality, the complex structure is disadvantageous again in respect of the machine maintenance, which requires frequent readjustments of jaws of the vise in particular and other machine parts as well.
Another difficulty to be particularly noted derives from the structural feature such that the jaws of the vise are reciprocated to open and close through a cam and spring mechanism, and it resides in that the reciprocation of jaws not only gives rise to extremely high noises but also sets a limitation to the speed-up of the machine operation where required.
The present invention has effectively cancelled these and other difficulties with the current web folding machines, and in principle the invention proposes to utilize, in lieu of the reliance in the prior art on such a mechanical means as comprising the combination of a vise and a tacker, the force of negative pressures or suction applied through roll surfaces to web pieces for delivering the same end, in operative combination with a folding bar member, folding the same. In practice, the invention utilizes suction rolls in place of the prior art rolls having a vise and tacker mechanism, to make the entire structure of the folding machine simple, easy and inexpensive to manufacture and maintain, and effectively answer the need for enhancing the machine efficiency, with mechanical or operational noises remarkably reduced. Also, the employment of suction rolls in accordance with the present invention has greatly restricted the number of parts in current machines, such as springs and cams indispensable to a vise-and-tacker mechanism.